Wait a few more hours (max 24). If you still did not receive it, simply contact Paypal and give them all the info's you can.
lol 1k accounts go far more than 20$ So even hes completely idiot or you (most likely) got scammed.
http://www.youtube.com/t/termsYou agree not to use the Service for any of the following commercial uses unless you obtain YouTube's prior written approval:
* the sale of access to the Service;
* the sale of advertising, sponsorships, or promotions placed on or within the Service or Content; or
* the sale of advertising, sponsorships, or promotions on any page of an ad-enabled blog or website containing Content delivered via the Service, unless other material not obtained from YouTube appears on the same page and is of sufficient value to be the basis for such sales.
If it's been a matter of a few hours it's really not necessary to call it a scam yet, at least wait a day or 2 not an hour.
If I were scamming I wouldn't be sending any youtube accounts. Though what you bought it for was ridiculously cheap and shoulda been a sign right there, even so if you got 500 working accounts for that price isn't that still pretty good?